The invention relates in general to rotary drum filters. More specifically, the invention relates to an improved deck design that increases filter efficiency for corrugated deck type rotary drum filters.
Rotary drum filters are used in the pulp and paper industry to filter liquid out of pulp. The filters include a cylindrically shaped drum that is typically constructed of metallic and/or fiberglass materials. In operation, the drum is partially submerged in a vat containing a paper pulp stock. The outer surface of the drum acts a filtering medium or structure that passes liquid as the drum is rotated. Pulp is retained on, and subsequently removed from, the outer surface of the drum.
The drum includes a cylindrical shell that is supported on the inside by flyrings and is closed at each end by end supports. Longitudinal grids are installed perpendicular to the outside surface or deck of the shell in a predetermined spaced relationship. The longitudinal divider grids or rib elements extend along the entire length of the deck and define drain channels that empty into vacuum shut off sections, referred to as buckets, located at the periphery of the deck.
In some filters, referred to as "open channel filters", the longitudinal grids are covered with a backing wire that forms the outer surface of the drum. Liquid can pass through the spaces provided between the backing wire while pulp is retained on the surface of the wire. In other filters, referred to as "corrugated deck filters", an example of which is disclosed in U.S. Pat. No. 3,837,499, the contents of which is herein incorporated by reference, the longitudinal grids are covered with a corrugated material that forms the outer surface of the drum. The corrugated material includes drain slits that correspond to the drain channels. Each drain slit permits liquid to pass through the corrugated material to a single drain channel while pulp is retained on the surface of the corrugated material. It is an object of the present invention to increase the filtering efficiency of corrugated deck type rotary filters.